Is there life on Mars? Not if we destroy it with poor space hygiene | Mars

Next month, three new spacecraft arrive at Mars. Two represent firsts for their countries of origin, while the third opens a new era of Mars exploration. The first is the UAE’s Emirates Mars Mission, also known as Hope, which enters orbit on 9 February. Shortly after, China’s Tianwen-1 settles into the red planet’s gravitational grip and in April will deploy a lander carrying a rover to the surface.

Both of these missions are groundbreaking for their countries. If they are successful, their makers will join the US, Russia, Europe and India in having successfully sent spacecraft to Mars. However, it is the third mission that is destined to capture the most headlines.

On 18 February, around 8pm GMT, Nasa will attempt to land the car-size rover Perseverance in Jezero crater. It’s got a long list of science objectives to work through. “We want to get a fuller understanding of how Mars formed as a planet,” says Sanjeev Gupta of Imperial College London, who is part of the Perseverance science team.

On Earth, the constant shifting of the crust has mostly destroyed the very first surface rocks to form, but on Mars the oldest rocks are preserved, so there is an unbroken record stretching back more than four billion years. As well as telling us about the history of the planet’s formation, those primeval rocks could also contain clues as to whether life ever began on the red planet.

Yet what makes Perseverance unique is that it is also the first part of an ambitious 10-year plan between Nasa and the European Space Agency (Esa) to bring Martian rocks to Earth in around 2031.

“Scientists really want rocks from Mars back on Earth,” says Gupta. Samples can be analysed much more thoroughly on Earth than using even the most sophisticated Mars rover. And because laboratory techniques improve constantly, they can continue to be inspected year after year for new discoveries.

The value of sample return was demonstrated in the 1970s when the analysis of moon rocks brought back by the Apollo astronauts changed our understanding of the solar system’s history and formation.

To replicate this success for Mars, Perseverance is equipped with more than 30 canisters, into which interesting-looking rocks will be loaded and then cached on the surface. If all goes well, a European rover built at Airbus Defence and Space in Stevenage will arrive on Mars in 2028 to collect the canisters. It will load them into a Nasa spacecraft known as the Mars Ascent Vehicle, which will blast them to a rendezvous with the European supplied Earth Return Orbiter that will bring the samples to Earth.

Whereas the lunar samples of the 1970s were from a barren world, Mars could once have been a habitable planet. So key investigations will involve looking for evidence of past – or possibly present – life and that is a whole new ballgame.

“If you discover signs of life on Mars, you want to know that’s Martian life, right? You don’t want to accidentally discover E coli bacteria that hung on to your spacecraft,” says Casey Dreier, chief advocate and senior space policy adviser for the Planetary Society, a non-profit organisation for space advocacy based in Pasadena, California.

To keep the scientific results as pure as possible, spacecraft and equipment are cleaned with chemical solvents or by heating.

“When building a mission to Mars, you have to apply these biological controls that go beyond what we typically use for satellites that we build for, say, Earth observation,” says Gerhard Kminek, a planetary protection officer for Esa. He’s been working since 2004 to make sure such precautions become standard practice at Esa for anything going to Mars – including the Rosalind Franklin rover that will launch in 2022 and which carries life-detection equipment.

From working on Rosalind Franklin, European aerospace companies Airbus and Thales Alenia Space now have biologically controlled cleanrooms in which to build almost completely sterile spacecraft. “We’re in a very good position,” says Kminek, so much so that Nasa sent a delegation late last year to visit the facilities and learn from them.

Kminek is also spearheading studies into the kind of containment facility needed to hold Mars samples on Earth. Working with organisations such as Public Health England, the Porton Down laboratory and the European Centre for Disease Prevention and Controls, Thales UK and the University of Leicester have already built a prototype “double wall isolation chamber” under an Esa contract.

Such precautions are known as planetary protection, which is split into two components. Forward contamination is the introduction of Earth life on to other worlds; backwards contamination is concerned with the possibility,…